A New ¹⁴C Calibration Data Set for the Last Deglaciation Based on Marine Varves

Varved sediments of the tropical Cariaco Basin provide a new 14 C calibration data set for the period of deglaciation (10,000 to 14,500 years before present: 10–14.5 cal ka bp). Independent evaluations of the Cariaco Basin calendar and 14 C chronologies were based on the agreement of varve ages with the GISP2 ice core layer chronology for similar high-resolution paleoclimate records, in addition to 14 C age agreement with terrestrial 14 C dates, even during large climatic changes. These assessments indicate that the Cariaco Basin 14 C reservoir age remained stable throughout the Younger Dryas and late Allerød climatic events and that the varve and 14 C chronologies provide an accurate alternative to existing calibrations based on coral U/Th dates. The Cariaco Basin calibration generally agrees with coral-derived calibrations but is more continuous and resolves century-scale details of 14 C change not seen in the coral records. 14 C plateaus can be identified at 9.6, 11.4, and 11.7 14 C ka bp, in addition to a large, sloping “plateau” during the Younger Dryas (∼10 to 11 14 C ka bp). Accounting for features such as these is crucial to determining the relative timing and rates of change during abrupt global climate changes of the last deglaciation.